Methyl methacrylate copolymers

ABSTRACT

Copolymers prepared from methyl methacrylate, electron deficient monomers, for example N-aryl maleimides and other ethylenically, unsaturated monomers copolymerisable therewith.

United States Patent Nield 5] *July 11, 1972 s41 METHYL METHACRYLATE 51Int. Cl. ..C08f 19/10 COPOLYMERS [58] Field of Search ..260/78 R, 78 UA,78.5 NR, 85.7, 260/80.6, 80.8, 80.81, 86.1, 86.7 [72] Inventor: EricNield, Watton-at-Stone, England [73] Assignees: Imperial ChemicalIndustries Limited, [56] References Cited England; UNITED STATES PATENTSNotice: The portion of the term of this patent sub- 3 480 598 H 1969 Id260 78 5 sequent to Nov. 25, has been dis- 1 y I I6 a: PrimaryExaminer-Joseph L. Schofer [22] Filed: June 9, 1970 AssistantExaminer-John Kight, III

I AnorneyCushman, Darby & Cushman [21] Appl. No.: 44,879

' Q 57 ABSIRA T Related US. Application Data 1 C Copolymers preparedfrom methyl methacrylate, electron [63] q -P of deficient monomers, forexample N-aryl maleimides and other 1964 commuanon'm'pan of 781,673ethylenically, unsaturated monomers copolymerisable 16, 1968' therewith.

[52] US. Cl. ..260/78 UA, 260/78.5 R, 260/80.6,

7 Claims, No Drawings METHYL METHACRYLATE COPOLYMERS This application isa continuation-in-part of application, Ser. Nos. 360,073, now abandonedand 781,673, filed 15th Apr. 1964 and 16th Oct. 1968 respectively. Ser.No. 781,673, now U.S. Pat. No. 3,480,598 being a continuation of Ser.No. 463,869 filed 14th June 1965, and now abandoned.

The present invention relates to new copolymers, particularly tocopolymers of N-substituted maleimide and methyl methacrylate.

It has been proposed to make copolymers of maleimide and N-alkyl orN-aralkyl maleimides with various other monomers. Quite often it isfound that when such copolymers are prepared the copolymer is morebrittle than the homopolymer obtainable from the monomer with which saidmaleimide or N-substituted maleimide is copolymerized, even although thecopolymer may have better physical properties than the homopolymer incertain other respects. It is also often found that the water absorptionis appreciably increased as compared with the homopolymer of the othermonomer.

Polymethyl methacrylate is an organic polymeric material of considerablecommercial value. It has great utility and is widely used for manydifferent applications. It is a thermoplastic material which means thatit softens and can be shaped or moulded when heated to hightemperatures. For some purposes it would be an advantage if a polymerhaving all the useful properties of polymethyl methacrylate but having ahigher softening point could be produced. It is however particularlyimportant that such an increase should not be accompanied by an increasein the brittleness nor water absorption of the polymer.

It has been proposed to make certain copolymers of methyl methacrylateand a-methyl styrene to achieve this end, but the production of suchcopolymers is made difficult by the slow rate of polymerization ofa-methyl styrene and the consequent difficulty of avoiding heterogeneityin the products.

We have now found that improvements in this effect can be achieved byproviding copolymers of methyl methacrylate, an electron deficientmonomer and another ethylenically unsaturated monomer.

According to the present invention we provide a copolymer of (i) methylmethacrylate, (ii) a polymerizable monomer that is moreelectron-deficient than methyl methacrylate, selected from the groupconsisting of maleic anhydride, maleimide and its N-substitutedderivatives, and (iii) another ethylenically unsaturated compoundselected from the group consisting of tx-methyl styrene, vinyl acetate,esters of acrylic acid, esters of methacrylic acid other than methylmethacrylate, vinyl chloride, vinylidene chloride, styrene and halogensubstituted styrenes, vinyl and isopropenyl ethers and dienes, which iscopolymerizable with both said methyl methacrylate and saidelectron-deficient monomer, in which:

when the said electron-deficient monomer is N-aryl maleimide thecopolymer consists essentially of from 65 to 99 percent by weight ofmethyl methacrylate units, 1 to 35 percent by weight of N-aryl maleimideunits and to percent by weight of units of said ethylenicallyunsaturated compound,

and when the said other ethylenically unsaturated compound is a-methylstyrene the copolymer consists essentially of from 45 to 99 percent byweight of methyl methacrylate units, and from 55 to 1 percent by weightof a-methyl styrene units and units of said electron-deficient monomertaken together, said electron deficient monomer units being in theproportion of 0.05 to 2 moles per mole of said a-methyl styrene units.

We have also found that improvements are achieved by providingcopolymers of methyl methacrylate and N-aryl maleimides.

According to another aspect of the present invention we also providecopolymers of methyl methacrylate and N-aryl maleimides, containing from65 to 99 percent by weight of methyl methacrylate units, 1 to 35 percentby weight of units derived from said N-aryl maleimide, and 0 to 15percent by weight of units derived from any other ethylenicallyunsaturated compound copolymerizable with both said methyl methacrylateand said N-aryl maleimide. We also provide a process wherein theingredients to form the copolymers are polymerized together.

It will be appreciated that the nature of the copolymers will bedetermined at least in part by the relative proportions of the componentmonomers. Therefore, while we provided a wide range of usefulcopolymers, in order to obtain a copolymer which is a modified form ofpolymethyl methacrylate that is mouldable and shapeable in much the sameway as polymethyl methacrylate, we prefer to limit the proportion ofN-aryl maleimide in order to obtain this effect and also thehereinbefore mentioned advantages of increased softening point withoutsubstantial increase in water absorption as compared withpolymethylmethacrylate and, where possible, an avoidance of asubstantial increase in brittleness as compared with polymethylmethacrylate. Therefore in order to get the best combination of highsoftening point, no substantial increase in brittleness or waterabsorption, and good moulding properties, as compared in order to obtainthis effect and also the hereinbefore mentioned advantages of increasedsoftening point without substantial increase in water absorption ascompared with polymethyl methacrylate, in a preferred form of ourinvention we provide copolymers of methyl methacrylate and N-arylmaleimides, containing from to percent by weight of methyl methacrylateunits, 5 to 20 percent by weight of N-aryl maleimede units, and 0 to 15percent by weight of units derived from any other ethylenicallyunsaturated compound copolymerizable with both said methyl methacrylateand N-aryl maleimide.

It will be appreciated that in our copolymers the N-aryl maleimide unitsmay be derived from a mixture of maleimides.

N-aryl maleimides that we have found to be particularly suitable for usein our invention include N-phenyl maleimide and substituted derivativesthereof in which at least one of the aromatically bound hydrogen atomshas been substituted by a halogen atom, a nitro group, a nitrile group,aryl, aryloxy, aralkyl, aralkoxy, aryloxy alkyl or an alkyl or alkoxygroup containing from one to four carbon atoms. It will be appreciatedthat these substituted derivatives of N-phenyl maleimide may themselvesbe substituted. Other N-aryl maleimides that may be used includeN-a-naphthyl maleimide and derivatives thereof.

Of the N( halogen-substituted phenyl) maleimides we prefer the bromoorchloro-substituted derivatives because of their ready availability.Examples are N-(Z-chloro-phenyl) maleimide, N-(3-chloro-phenyl)maleimide, N-(4-chlorophenyl) maleimide, N-(4-bromo-phenyl) maleimide,N- (2,4,6-trichloro-phenyl) maleimide and N-(2,4,6-tribromophenyl)maleimide. Other N-(substituted phenyl) maleimides which may be usedinclude N-(Z-methyl-phenyl) maleimide, N-(3-methyl-phenyl) maleimide,N-(4-methyl-phenyl) maleimide, N( Z-t-butyl-phenyl) maleimide, N(S-t-butyl-phenyl) maleimide, N( 4-t-butyl-phenyl) maleimide, N(2,6-dimethylphenyl) maleimide, N (2-nitro-phenyl) maleimide, N( 3-nitro-phenyl) maleimide, N-(4nitro-phenyl) maleimide, N-(2,4-dinitro-phenyl) maleimide, N( 2-methoxy-phenyl) maleimide,N-(3-methoxy-phenyl) maleimide, N-(4-ethoxy-phenyl) maleimide,N-(4-cyano-phenyl) maleimide, N( 2-methyl-4- chloro-phenyl) maleimide,N-4-phenyl phenyl maleimide, N- 4-phenyloxy phenyl maleimide, N-4-benzylphenyl maleimide, N-4-benzyloxy phenyl maleimide, N-4-phenoxy methylphenyl maleimide and N-2-chloro4-phenoxy phenyl maleimide.

We prefer to use N-(substituted-phenyl) maleimides having a substituentin the 2-position on the phenyl radical attached to the nitrogen atom,because the use of such substituted maleimides leads to the productionof copolymers with a greater freedom from color than is possible withother substituted N-phenyl maleimides. N( 2-chloro-phenyl) maleimide isparticularly effective in this regard. Where a copolymer having goodflame resistance is required, it is advantageous to use an N-arylmaleimide containing a high proportion by weight of chlorine or brominesubstituents.

The third monomer which may provide units forming from to 15 percent byweight of the copolymer is preferably one that has no adverse effect onthe properties of the copolymer, and normally the reason for includingsuch a third copolymerizable component is to modify the properties ofthe copolymer in some desirable manner, e.g. by increasing the flowproperties when heated to moulding temperatures, or to reduce anyresidual color in the copolymer, or by using a polyfunctional monomer tointroduce some degree of crosslinking. Suitable monomers for thesepurposes include vinyl esters, esters of acrylic acid e.g. methyl andethyl acrylate, esters of methacrylic acid other than methylmethacrylate, e. g. butyl methacrylate and ethyl hexyl methacrylate,vinyl chloride, vinylidene chloride, styrene, a-methyl styrene and thevarious halogen substituted styrenes, vinyl and isopropenyl ethers,dienes such as l,3-butadiene and divinyl benzene. Reduction in color ofthe copolymer can be effected by reducing the residual maleimide in thecopolymer and this is best effected by using as the thirdcopolymerizable component a monomer which is electron rich e.g. a vinylether, vinyl acetate, styrene or a-methyl styrene.

The copolymer can be prepared by any of the well known polymerizationprocesses, i.e. in bulk, in solution, in aqueous emulsion or in aqueoussuspension. When using a solvent process the organic compound used asthe solvent should not react with any of the monomers, and preferablyshould have little or no chain transfer effect on the polymerizationreaction. Our copolymers may also be made in bulk by the continuousprocess described in our British specification, No. 875,853 and our U.S.specification, No. 3,234,303.

The polymerization may be effected at any desired temperature,preferably in the presence of a free radical yielding catalyst that isactive at the polymerization temperature. A particularly usefultemperature range is 0 to 120 C. and catalysts suitable for use in thisrange include aa-azo-diisobutyronitrile and benzoyl peroxide or otherorganic peroxides and hydroperoxides. Normally the amount of catalystrequired to give useful results lies between 0.05 and 2 percent byweight of the polymerizable monomers.

Ancillary ingredients may be added at any convenient stage during themanufacture of the copolymers or they may be blended with the copolymerafter it has been made. Examples of such ingredients include fillers(e.g. glass fibers), pigments, heat and light stabilizers, plasticizers,lubricants, flame retardants and mould release agents. The copolymersmay be blended with other polymeric materials e.g. synthetic rubbers.

Our copolymers are extremely useful for moulding many different kinds ofarticles, particularly articles that may have to be exposed torelatively high ambient temperatures. Further the strength and clarityof our transparent copolymers whether prepared as glass-like sheets oras moulding powders makes them suitable for use as windows or in anyother shaping or moulding where either transparency or a bright coloredform is required and where the shaping or moulding is to be exposed torelatively high ambient temperatures.

The properties of our copolymers may be improved, particularly in regardto impact resistance, and craze resistance by incorporating thereinrubbery polymeric materials e.g. rubbery copolymers of butadiene-l,3 andstyrene, methyl methacrylate or acrylonitrile; saturated polymericrubbers e.g. polyethyl acrylate and the rubbery copolymers of the loweralkyl acrylates e.g. those containing 1 to 4 carbon atoms in the alcoholmoiety and the rubbery copolymers of ethylene with for example vinylacetate and methyl methacrylate. The extrusion properties of suchcompositions may be improved by using these rubbery materials in asubstantially cross-linked form such as may be obtained for example bymasticating the copolymers of butadiene, or by including a small amountof a cross-linking monomer in the polymerization recipe used for thepreparation of the rubbery polymeric material. Useful amounts of theserubbery materials may be from to 100 percent by weight preferably 20 to45 percent based on the weight of the copolymer of methyl methacrylateand the N- aryl maleimide.

The rubber may be included by any conventional mixing technique.Alternatively the ingredients to form the rubber may be polymerized inthe presence of the already formed copolymer of methyl methacrylate andN-aryl maleimide. Alternatively the ingredients to form the copolymer ofmethyl methacrylate and N-aryl maleimide may be polymerized in thepresence of the already formed rubber.

In a preferred form of our invention we therefore provide a compositioncomprising our copolymer of methyl methacrylate and N-aryl maleimidewith from 10 to 100 percent by weight based on the weight of thecopolymer of a rubbery polymeric material.

Another object of the present invention is the provision of copolymersof methyl methacrylate and a-methyl styrene having an increasedsoftening point which can be made by a relatively rapid process.

According to yet another aspect of the present invention we provide apolymeric product of a methyl methacrylate, amethyl styrene and at leastone polymerizable monomer that is more electron deficient than methylmethacrylate and selected from the group consisting of maleic anhydrideand maleimide and its N-substituted derivatives, the product containingfrom 45 to 99 percent by weight of methyl methacry late units, and from55 to 1 percent by weight of a-methyl styrene units and units of saidelectron deficient monomer taken together, said electron deficientmonomer units being in the proportion of 0.05 to 2 moles per mole ofsaid a-methyl styrene units.

Further in accordance with our invention we provide a process for theproduction of polymeric products in which a mixture of monomers ispolymerized, said mixture consisting essentially of 45 to 99 percent byweight of the mixture of methyl methacrylate, and from 55 to 1 percentby weight of said mixture of a-methyl styrene and one or more monomersmore electron deficient than methyl methacrylate, said electrondeficient monomer or monomers being in the proportion of 0.05 to 2 molesper mole of said a-methyl styrene.

In general we prefer that the electron deficient monomer should be in anamount not greater than one mole per mole of a-methyl styrene.

We prefer to use methyl methacrylate because polymeric products based onmethyl methacrylate have the greatest utility as regards hardness andgeneral suitability for making moulded products, than any other alkylmethacrylate.

We prefer that methyl methacrylate units comprise from 55 to 95 percentby weight of our polymeric product because these proportions cover themost generally useful part of our range of products. More particularlywe prefer that the methyl methacrylate units should comprise from 60 topercent by weight of the product because within this range products haveproperties usually associated with polymethyl methacrylate. With lessthan 60 percent of methyl methacrylate the polymers tend to be brittle,and with greater than percent of methyl methacrylate an effectiveincrease in the softening point may not be achieved.

In order to determine whether a monomer is more electron deficient thanmethyl methacrylate, reference may be made to Journal of Polymer ScienceVolume 54, 1961, pages 411 455, particularly page 444. The monomerslisted are characterized by a factor e which is a copolymerizationparameter which depends upon the polar properties of the monomer.Accordingly electron deficient monomers which may be used in ourinvention are those which have a greater positive value of e" than thevalue of methyl methacrylate. We prefer that the value of e" for theelectron deficient monomer should be appreciably greater than the valuefor methyl methacrylate, which is 0.40. Thus we prefer to use electrondeficient monomers having a value of e greater than 0.8.

Where it is required that our polymeric products should have softeningpoints greater than that of polymethyl methacrylate it is generallynecessary that the electron defi' cient monomer should be capable(actually or theoretically) of forming a homopolymer that has asoftening point substantially the same as, or greater than that ofpolymethyl methacrylate. Examples of such monomers are maleimide and itsNasubstituted derivatives, maleic anhydride, and methylene malonicesters.

Examples of other monomers that may be used in our invention but whichdo not necessarily yield polymeric products having softening pointsgreater than that of polymethyl methacrylate include methylacrylate,methacrylic acid, acrylic acid, n-octyl acrylate, butyl acrylate, vinyltrifluoroacetate, acrylamide, diethyl fumarate and dimethyl fumarate.

It will be appreciated that our copolymers can include a small amount ofa monomer which is less electron deficient than methyl methacrylate inorder to obtain some additional advantageous effect whether or notaccompanied by an improvement in the softening point provided that theadvantages of the presence of the a-methyl styrene and the electron deficient monomer are not substantially reduced.

The methyl methacrylate and a-methyl styrene copolymers hereinbeforedescribed may also be blended with normal ancillary ingredients, e. g.dyestuffs, pigments, plasticizers, stabilizers, fillers and otherpolymeric material. Rubber-like polymeric materials may usefully beadded to increase the impact resistance of our copolymers.

Our invention is illustrated but in no way limited by the followingExamples in which all parts are expressed by weight.

EXAMPLE 1 Methyl methacrylate 90 parts, N-phenyl maleimide parts, andbenzoyl peroxide 0.1 part, were mixed together in a vessel and heated toform a syrup.

A cell was prepared from two rectangular sheets of glass separated fromeach other by a distance of 0.32 cms. by means of a flexible gasketaround the periphery of the glass sheets. The glass cell was filled withthe syrup and then maintained at 70 C. for 65 hours and then at 110 Cfor one hour. The glass plates were separated leaving a sheet of solidpolymer which was found to have a reduced viscosity of 6.2 (measured asa 0.5 percent solution in chloroform at 25 C.) and a Vicat softeningpoint of 129 C. When this polymer was saturated with water the Vicatsoftening point fell to 1 14 C.

The sheet so made was transparent, and could be shaped into usefularticles.

For comparison a sheet of polymethyl methacrylate made in a similarmanner had the following properties:

Reduced Viscosity 10.96 Vicat softening point l23.5 C Vicat softeningpoint after saturation with water 104.1C

EXAMPLE 2 The process of Example 1 was repeated using the followingmaterials:

N-o-tolyl maleimide 10 parts Methyl methacrylate 90 parts Benzoylperoxide 0.1 part A polymer was obtained having reduced viscosity of 6.6(measured as a 0.5 percent solution in chloroform at 25 C), and a Vicatsoftening point of 128 C. When a piece of this polymer was saturatedwith water its Vicat softening point fell to 113. The sheet so made wastransparent and free from color.

EXAMPLE 3 Example 2 was repeated with varying amounts of N-o-tolylmaleimide but carrying out the polymerization for hours at 70 C.followed by heating at 1 10 C. for 2 hours. The following table showsthe amounts of monomers used, and the reduced viscosities and Vicatsoftening points of the polymers obtained.

Reduced N-o-lolyl Methyl viscoslty (0.5% solution Vicat Softening LIImaleimide methacrylate in chloroform Point C.

Parts Parts at 25 C.)

EXAMPLE 4 A syrup was prepared as in Example 1 from the followingmaterials:

Methyl methacrylate 22.5 parts N-Z-chlorophenyl maleimide 2.5 partsBenzoyl peroxide 0.025 part The syrup was then poured into a cell formedby two glass plates spaced apart at a distance of 0.32 cms. by means ofa flexible gasket and the filled cell was maintained at 65 70 C for 18hours and then at C. for one hour. The polymer had a reduced viscosity(measured as a 0.5 percent solution in chloroform at 25 C.) of 8.6 and aVicat softening point of 127 C. When saturated with water the Vicatsoftening point fell to 112 C.

EXAMPLE 5 The procedure of Example 4 was repeated using the followingmaterials:

Methyl methacrylate 22.5 parts N-4-chloropheny1 maleimide 2.5 partsBenzoyl peroxide 0.025 part A cell was similarly filled and maintainedat 65 C for 22 hours and then at 1 10 C. for two hours. The resultingpolymer had a reduced viscosity as hereinbefore defined of 8.6 and aVicat softening point of 126 C.

EXAMPLE 6 A copolymer sheet was made exactly as in Example 5 using thefollowing materials:

Methyl methacrylate 23.75 parts N-a-naphthyl maleimide 1.25 partsBenzoyl peroxide 0025 part The polymer had a reduced viscosity, ashereinbefore defined of 8.26, and a Vicat softening point of C.

EXAMPLE 7 This Example comprises the properties of certain N-arylmaleimide/methyl methacrylate copolymers with copolymers of methylmethacrylate and maleimide, N-methyl maleimide and N-benzyl maleimiderespectively. The copolymers were prepared as described in Example 6 andthe properties of the copolymers are shown in the following Table:

parts by weight 90 parts N-benzyl maleimide 124C 2.72% 104.6C 10 partsby weight The water absorption was measured by immersing a piece of thepolymer in boiling water until it was saturated with water and thenmeasuring its change in weight.

As can be seen from this table the three N-aryl maleimides illustratedvis. N-phenyl maleimide. N-o-tolyl maleimide and N-2-chloro-phenylmaleimide showed a fall in Vicat softening point but not nearly as greata fall as that shown by maleimide, the N-alkyl maleimide (N-methylmaleimide) and the N-aralkyl maleimide (N-benzyl maleimide). Further theamount of water absorbed was less in the case of the three Narylmaleimide copolymers than in the case of the other three copolymers. Thelatter three copolymers became hazy when they absorbed water whereas theformer copolymers remained transparent.

EXAMPLE 8 The following materials were added to a stirred autoclave:

Methyl methacrylate parts N-phenyl maleimide 5.19 parts Water 100 partsPotassium persulphate 0.5 part Sodium lauryl sulphate 0.5 part Themonomers were dispersed by vigorous stirring and maintained at 60 C. forabout 24 hours. A stable polymer dispersion was obtained from which thepolymer was precipitated by the addition of a saturated solution ofsodium chloride. The polymer thus obtained was filtered and thoroughlywashed with water and then dried. The polymer had a reduced viscosity(as hereinbefore defined) of 9.1 and a Vicat softening point of l33.5 C.

EXAMPLE 9 A polymerization process was carried out as in Example 8 usingthe following materials:

Methyl methacrylate 15 parts N-o-tolyl maleimide 5.61 parts Water 100parts Potassium persulphate 0.5 part Sodium lauryl sulphate 0.5 part Thedried polymer had a reduced viscosity as hereinbefore described of 9.6and a Vicat softening point of 145 C. I

EXAMPLE 10 The following materials were fed into a vessel:

Methyl methacrylate 5 parts N-phenyl maleimide 1.73 parts Methanol 16parts aa-azodiisobutyronitrile 0.05 part The vessel was sealed andevacuated and maintained at 60 C. for 24 hours. The resulting polymerwas filtered from the methanol, dissolved in chloroform, reprecipitatedinto ether, filtered and dried in vacuo. It was found to have a reducedviscosity of 0.71 (as hereinbefore defined) and a Vicat softening pointof 140.5 C.

EXAMPLE 1 1 A solution of N-o-tolyl maleimide (10 parts) and benzoylperoxide (0.7 part) in methyl methacrylate (90 parts) was dispersed inan equal volume of a buffered solution of sodium polymethacrylate (0.06part) in water 100 parts). The dispersion was placed in a flask equippedwith a reflux condenser and a stirrer and was heated to refluxtemperature until polymerization was complete, as shown by a maximum inthe temperature of the reactants.

The product consisted of spherical granules. After water washing,filtering and drying a compression moulding was made. The Vicatsoftening point was found to be 125 C. The reduced viscosity of thepolymer (as hereinbefore defined) was approximately 2.0.

EXAMPLE 1 2 A solution of N-Z-chlorophenyl maleimide (10 parts) at!-azodiisobutyronitrile (0.2 part) and tertiary lauryl mercaptan (2.0parts) in methyl methacrylate (90 parts) was dispersed in a solution ofPolyox" WSR 301, a polyethylene glycol dispersing agent (0.4 part) inwater (100 parts) and polymerized as in Example 1 1.

The product had a reduced viscosity of 1.5 (hereinbefore described) anda compression moulding had a Vicat softening point of 128 C.

EXAMPLE 13 Syrup was formed from wmethyl styrene (1.2 part), N-otolylmaleimide (1.9 part), methyl methacrylate (22 parts), benzoyl peroxide(0.025 part) and heated at ca. 70 C, in a glass cell for 20 hours andthen for one hour at 1 10 C. The resulting polymer was transparent andhad a reduced viscosity of 2.7 and a Vicat softening point of 130 C.

EXAMPLE 14 A solution of N-2-chlorophenyl maleimide (10 parts), styrene(10 parts) and aa'-azodiisobutyronitrile (0.1 part) and tertiary laurylmercaptan (2.0 parts) in methyl methacrylate, parts) was dispersed in anequal volume of a buffered solution of sodium polymethacrylate (0.06part) in water 100 parts) and polymerized as in Example 1 1. The producthad a reduced viscosity of 1.2 and a compression moulding had a Vicatsoftening point of 126 C.

EXAMPLE 15 A solution of N-2-chlorophenyl maleimide 10 parts), vinylisobutyl ether (5 parts), lauroyl peroxide (0.5 part) and laurylmercaptan (0.3 part) in methyl methacrylate parts) was dispersed in anequal volume of a solution of Polyox WSR 301, a polyethylene glycoldispersing agent (0.4 part) in water parts) and polymerized as inExample 1 1.

The product had a reduced viscosity of 1.0 and a Vicat softening pointof 122 C. (on a compression moulding).

EXAMPLE 16 A solution of N-2-chlorophenyl maleimide 10 parts) amethylstyrene (15 parts) and aa'-azodicyclohexane carbonitrile (0.2 part) inmethyl methacrylate (75 parts) was dispersed in an equal volume ofPolyoxWSR 301 (0.4 part) in water (100 parts). The mixture was placed in astainless steel pressure vessel equipped with a stirrer and was stirredat a temperature of 100 C. for 2 hours.

The product, consisting of spherical granules, had a reduced viscosityof 0.35 and a compression moulding had a Vicat softening point of 122 C.

EXAMPLE 17 To this latex (1515. parts about 16 percent solids) was addedmethyl methacrylate (860 parts), tertiary lauryl .mercaptan (20 parts),lauroyl peroxide (2.5 parts) and N-2- chlorophenyl maleimide (95.5parts). When the aryl maleimide had dissolved, water (500 parts) wasadded. To this mixture was added hydrated aluminum sulphate (0.35 part)dissolvedin water (20 parts).and after 5 minutes further stirring,sodium polyacrylate (0.6 part), anhydrous disodium phosphate (1.3 parts)andmonosodium phosphate dihydrate (4.6 parts) were added and the .wholecontents were heated to reflux temperature (82 C.).

After holding at 82 C. for 50 minutes the temperature rose spontaneouslyto 90 C., after heating to 97 C. and holding for minutes, the polymerparticles were centrifuged off, washed, dried and injection moulded.

The translucent-grey mouldings produced had superior falling weightvimpact strength, Vicat softening point and 'detergent craze resistancecompared withinjection moulded polymethyl methacrylate, or methylmethacrylate/N-Z-chlorophenyl maleimide copolymer or a polymethylmethacrylatepolyethylacrylate rubber blend prepared as above but withthe omission of N-Z-chloro-phenyl maleimide.

EXAMPLE 18 A solution of methyl methacrylate (70 parts), a-methylstyrene parts) and N-o-chlorophenyl maleimide (10 parts) was emulsifiedin water (150 parts) containing sodium lauryl sulphate (0.15 part) andpotassium'persulphate (0.38 part). The mixture was heated to 80 C.(reflux) and held there; after 50 minutes the temperature rosespontaneously to 89 C.On raising the temperature to, 100 C. only verysmall quantities of a-methyl styrene were stripped off, showing thatpolymerization was substantially complete.

A similar polymerization using. no aryl maleimide took four hours toreach 90 percent polymerization and no spontaneous temperature rise wasnoted.

EXAMPLE 1 1 9 The following mixture wasprepared and warmed gently toform a syrup:

Maleic anhydride l1 pans a-Methyl styrene 14 parts Methyl methacrylate22.5 parts Benzoyl peroxide 0.25 part The syrup thus obtained waspouredinto acell formed by two parallel flat sheets of glass spaced apart bymeans of a flexible peripheral gasket a distance of one-eighth inch. Thefilledcell was maintained at-6570 C. for 17 hours and then at 110 C. for2 hours. The glass plates were then separated from the sheet of solidpolymer formed by this process which was colorless and transparent andhad a Vicat softening point of 119 C.-and a reduced viscosity of 1.43measured as a 0.5 percent solution in chloroform at C.

For comparative purposes this Example was repeated exactly as before butomitting the maleic anhydride and using 23.6 parts of methylmethacrylate in place of the 22.5 parts. It was not possible to form asyrup before filling the cell, and at the end of the process thecontents of the cell were in the form of a syrup and no solid polymerwas formed.

EXAMPLE 20 The following mixture was prepared and warmed gently to forma syrup:

Maleimide 11 parts a-Methyl styrene 14 parts Methyl methacrylate 22.5parts Benzoyl peroxide 0.25 part Acell was prepared and filled andheated exactly as described in Example 19. A solid sheet of polymer wasobtained that was transparent and colorless, had a Vicat softening pointof 129 C. and a reduced viscosity of 1.5 measured as a 0.5 percentsolution in chloroform at 25 C.

EXAMPLE 21 Water 100 parts Ethylene/maleic anhydride copolymer 0.03 partSodium dihydrogen phosphate 3 parts were placed in a five literautoclave which was then purged with nitrogen, and 100 parts ofpolymerizable monomers and 0.2 part of azodicyclohexanecarbonitrileadded. The 100 parts of polymerizable monomers were made up from varyingamounts of methyl methacrylate, a-methyl styrene and N-orthochlorophenylmaleimide. The polymerization time for each compositionwas measured and is recorded in the following table:

From the table we see that the copolymerization rate of methylmethacrylate and a-methyl styrene is substantially increased by thepresence of N-orthochlorophenylmaleimide which is more electrondeficient than methyl methacrylate.

EXAMPLE 22 Similar experiments to that of Example 21 were carried outusing maleimide or maleic anhydride in place of the N-orthochlorophenylmaleimide. The polymerization times for thesecompositions are shown in the following table:

Monomers Electron Poly- Poly- .methyl a-Methyl deficient merizationmerization metha- Styrene monomer Temp. Time acrylate parts 5 parts 5parts maleimide C min. 90 parts 5 parts 5 parts maleic 100C min.

anhydride 90 pans 10 parts 0 part 105C 300 min.

Again we see that the polymerization time is substantially reduced bythe addition of maleimide or maleic anhydride, both of which are moreelectron deficient than methyl methacrylate.

1 claim:

I. A copolymer of (i) methyl methacrylate, (ii) a polymerizable monomerthat is more electron-deficient than methyl methacrylate, selected fromthe group consisting of maleic anhydride, maleimide and itsN-substituted derivatives, and (iii) another ethylenically unsaturatedcompound selected from the group consisting of vinyl acetate, esters ofacrylic acid, esters of methacrylic acid other than methyl methacrylate,vinyl chloride, vinylidene chloride, styrene and halogen substitutedstyrenes, vinyl and isopropenyl ethers and dienes, which iscopolymerizable with both said methyl methacrylate and saidelectron-deficient monomer, in which:

when the said electron-deficient monomer is N-aryl maleimide thecopolymer consists essentially of from 65 to 99 percent by weight ofmethyl methacrylate units, 1 to 35 percent by weight of N-aryl maleimideunits and to 15 percent by weight of units of said ethylenicallyunsaturated compound.

2. A copolymer of methyl methacrylate and N-aryl maleimide consistingessentially of from 65 to 99 percent by weight of methyl methacrylateunits, 1 to 35 percent by weight of N aryl maleimide units, and 0 to 15percent by weight of units of other ethylenically unsaturated compoundscopolymerizable with both said methyl methacrylate and said N-arylmaleimide, said other ethylenically unsaturated compounds being selectedfrom the group consisting of vinyl acetate, esters of acrylic acid,esters of methacrylic acid other than methyl methacrylate, vinylchloride, vinylidene chloride, styrene, amethyl styrene and halogensubstituted styrene, vinyl and isopropenyl ethers, and dienes.

3. A copolymer according to claim 2 consisting essentially of from 80 to95 percent by weight of methyl methacrylate units, 5 to 20 percent byweight of N-aryl maleimide units and 0 to 15 percent of said any otherpolymerizable compound.

4. A copolymer according to claim 2 in which said N-aryl maleimide isselected from the group consisting of N-phenyl maleimide, substitutedderivatives thereof in which at least one of the aromatically boundhydrogen atoms has been substituted by a halogen atom or an alkyl groupcontaining from one to four carbon atoms and N-a-naphthyl maleimide.

5. A copolymer according to claim 4 in which in said N-aryl maleimide atleast one of the aromatically bound hydrogen atoms has been substitutedby a chlorine or bromine atom.

6. A copolymer according to claim 4 in which in said N- phenyl maleimidethe aromatically bound hydrogen atom attached to the 2-position on thephenyl radical has been substituted.

7. A copolymer according to claim 2 in which the monomer which providesresidues forming from O to 15 percent by weight of the copolymer isselected from styrene and vinyl ethers.

l l 4' t

2. A copolymer of methyl methacrylate and N-aryl maleimide consistingessentially of from 65 to 99 percent by weight of methyl methacrylateunits, 1 to 35 percent by weight of N-aryl maleimide units, and 0 to 15percent by weight of units of other ethylenically unsaturated compoundscopolymerizable with both said methyl methacrylate and said N-arylmaleimide, said other ethylenically unsaturated compounds being selectedfrom the group consisting of vinyl acetate, esters of acrylic acid,esters of methacrylic acid other than methyl methacrylate, vinylchloride, vinylidene chloride, styrene, Alpha -methyl styrene andhalogen substituted styrene, vinyl and isopropenyl ethers, and dienes.3. A copolymer according to claim 2 consisting essentially of from 80 to95 percent by weight of methyl methacrylate units, 5 to 20 percent byweight of N-aryl maleimide units and 0 to 15 percent of said any otherpolymerizable compound.
 4. A copolymer according to claim 2 in whichsaid N-aryl maleimide is selected from the group consisting of N-phenylmaleimide, substituted derivatives thereof in which at least one of thearomatically bound hydrogen atoms has been substituted by a halogen atomor an alkyl group containing from one to four carbon atoms and N- Alpha-naphthyl maleimide.
 5. A copolymer according to claim 4 in which insaid N-aryl maleimide at least one of the aromatically bound hydrogenatoms has been substituted by a chlorine or bromine atom.
 6. A copolymeraccording to claim 4 in which in said N-phenyl maleimide thearomatically bound hydrogen atom attached to the 2-position on thephenyl radical has been substituted.
 7. A copolymer according to claim 2in which the monomer which provides residues forming from 0 to 15percent by weight of the copolymer is selected from styrene and vinylethers.